The objective of this renewal proposal is the continued engineering and laboratory investigation of microporous membranes as blood compatible materials. We continued to study the bulk and surface characteristics of these materials, and their blood compatibility at the microporous interface. For this objective we have developed a sensitive method of visualization of protein adsorption on polymer surfaces, producing data which suggests the strength and extent of polymer-protein binding may be strongly influenced by surface microstructure. We popose to modify the surface microstructure, beginning with solid membrane, advancing to microporous membranes, so as to provide strong binding for a relatively non-thrombogenic protein, albumin. We have shown that subsequent binding of fibrinogen is inhibited by albumin pretreatment: surface coverage by fibrinogen is reduced from 80 to less than 20%. A systematic investigation of these surface modifications (microcrystallinity, surface interfacial energy) which optimize the long-term fibrinogen- and gamma globulin-rejecting characteristics of these surfaces is proposed. The investigation will culminate in thrombo-embolic implant studies of the materials and surface treatments of greatest promise.